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<meta name="description" content="A traditional tree view using TreeLayout with tri-state checkboxes showing partially checked subtrees."/> 
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<title>GoJS Tree View with Check Boxes</title>
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          <h1 class="mb-0 p-1 ">GoJS</h1>
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    <!-- * * * * * * * * * * * * * -->
    <!-- Start of GoJS sample code -->
    
    <script src="../release/go.js"></script>
    <div class="p-4 w-full">
    <script id="code">

    // This button assumes data binding to the "checked" property.
    go.GraphObject.defineBuilder("TriStateCheckBoxButton", function(args) {
      var button = /** @type {Panel} */ (
        go.GraphObject.make("Button",
          {
            "ButtonBorder.fill": "white",
            width: 14,
            height: 14
          },
          go.GraphObject.make(go.Shape,
            {
              name: "ButtonIcon",
              geometryString: 'M0 0 M0 8.85 L4.9 13.75 16.2 2.45 M16.2 16.2',  // a 'check' mark
              strokeWidth: 2,
              stretch: go.GraphObject.Fill,  // this Shape expands to fill the Button
              geometryStretch: go.GraphObject.Uniform,  // the check mark fills the Shape without distortion
              background: null,
              visible: false  // visible set to false: not checked, unless data.checked is true
            },
            new go.Binding("visible", "checked", function(p) { return p === true || p === null; }),
            new go.Binding("stroke", "checked", function(p) { return p === null ? null : "black"; }),
            new go.Binding("background", "checked", function(p) { return p === null ? "gray" : null; })
          )
        )
      );

      function updateCheckBoxesDown(node, val) {
        node.diagram.model.setDataProperty(node.data, "checked", val);
        node.findTreeChildrenNodes().each(function(child) { updateCheckBoxesDown(child, val); })
      }

      function updateCheckBoxesUp(node) {
        var parent = node.findTreeParentNode();
        if (parent !== null) {
          var anychecked = parent.findTreeChildrenNodes().any(function(n) { return n.data.checked !== false && n.data.checked !== undefined; });
          var allchecked = parent.findTreeChildrenNodes().all(function(n) { return n.data.checked === true; });
          node.diagram.model.setDataProperty(parent.data, "checked", (allchecked ? true : (anychecked ? null : false)));
          updateCheckBoxesUp(parent);
        }
      }

      button.click = function(e, button) {
        if (!button.isEnabledObject()) return;
        var diagram = e.diagram;
        if (diagram === null || diagram.isReadOnly) return;
        if (diagram.model.isReadOnly) return;
        e.handled = true;
        var shape = button.findObject("ButtonIcon");
        diagram.startTransaction("checkbox");
        // Assume the name of the data property is "checked".
        var node = button.part;
        var oldval = node.data.checked;
        var newval = (oldval !== true);  // newval will always be either true or false, never null
        // Set this data.checked property and those of all its children to the same value
        updateCheckBoxesDown(node, newval);
        // Walk up the tree and update all of their checkboxes
        updateCheckBoxesUp(node);
        // support extra side-effects without clobbering the click event handler:
        if (typeof button["_doClick"] === "function") button["_doClick"](e, button);
        diagram.commitTransaction("checkbox");
      };

      return button;
    });

    function init() {
      var $ = go.GraphObject.make;  // for conciseness in defining templates

      myDiagram =
        $(go.Diagram, "myDiagramDiv",
          {
            allowMove: false,
            allowCopy: false,
            allowDelete: false,
            allowHorizontalScroll: false,
            layout:
              $(go.TreeLayout,
                {
                  alignment: go.TreeLayout.AlignmentStart,
                  angle: 0,
                  compaction: go.TreeLayout.CompactionNone,
                  layerSpacing: 16,
                  layerSpacingParentOverlap: 1,
                  nodeIndentPastParent: 1.0,
                  nodeSpacing: 0,
                  setsPortSpot: false,
                  setsChildPortSpot: false
                })
          });

      myDiagram.nodeTemplate =
        $(go.Node,
          { // no Adornment: instead change panel background color by binding to Node.isSelected
            selectionAdorned: false,
            // a custom function to allow expanding/collapsing on double-click
            // this uses similar logic to a TreeExpanderButton
            doubleClick: function(e, node) {
              var cmd = myDiagram.commandHandler;
              if (node.isTreeExpanded) {
                if (!cmd.canCollapseTree(node)) return;
              } else {
                if (!cmd.canExpandTree(node)) return;
              }
              e.handled = true;
              if (node.isTreeExpanded) {
                cmd.collapseTree(node);
              } else {
                cmd.expandTree(node);
              }
            }
          },
          $("TreeExpanderButton",
            {
              width: 14,
              "ButtonBorder.fill": "whitesmoke",
              "ButtonBorder.stroke": "lightgray",
              "_buttonFillOver": "rgba(0,128,255,0.25)",
              "_buttonStrokeOver": null,
              "_buttonFillPressed": "rgba(0,128,255,0.4)"
            }),
          $(go.Panel, "Horizontal",
            { position: new go.Point(16, 0), margin: new go.Margin(0, 2, 0, 0), defaultAlignment: go.Spot.Center },
            new go.Binding("background", "isSelected", function(s) { return (s ? "lightblue" : "white"); }).ofObject(),
            $("TriStateCheckBoxButton"),
            $(go.TextBlock,
              { font: '9pt Verdana, sans-serif', margin: new go.Margin(0, 0, 0, 2) },
              new go.Binding("text", "key", function(s) { return "item " + s; }))
          )  // end Horizontal Panel
        );  // end Node

      // without lines
      //myDiagram.linkTemplate = $(go.Link);

      // with lines
      myDiagram.linkTemplate =
        $(go.Link,
          {
            selectable: false,
            routing: go.Link.Orthogonal,
            fromEndSegmentLength: 4,
            toEndSegmentLength: 4,
            fromSpot: new go.Spot(0.001, 1, 7, 0),
            toSpot: go.Spot.Left
          },
          $(go.Shape,
            { stroke: 'gray', strokeDashArray: [1, 2] }));

      // create a random tree
      var nodeDataArray = [{ key: 0 }];
      var max = 25;
      var count = 0;
      while (count < max) {
        count = makeTree(3, count, max, nodeDataArray, nodeDataArray[0]);
      }
      myDiagram.model = new go.TreeModel(nodeDataArray);
    }

    function makeTree(level, count, max, nodeDataArray, parentdata) {
      var numchildren = Math.floor(Math.random() * 10);
      for (var i = 0; i < numchildren; i++) {
        if (count >= max) return count;
        count++;
        var childdata = { key: count, parent: parentdata.key };
        nodeDataArray.push(childdata);
        if (level > 0 && Math.random() > 0.5) {
          count = makeTree(level - 1, count, max, nodeDataArray, childdata);
        }
      }
      return count;
    }
    window.addEventListener('DOMContentLoaded', init);
  </script>

<div id="sample">
  <div id="myDiagramDiv" style="border: 1px solid black; width: 400px; height: 500px"></div>
  <p>
    This sample is derived from the <a href="treeView.html" target="_blank">Tree View</a> sample.
    It adds the definition of the "TriStateCheckBoxButton" which is defined only to be used in a tree.
  </p>
</div>
    </div>
    <!-- * * * * * * * * * * * * * -->
    <!--  End of GoJS sample code  -->
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